“Why Don’t They Let Sharkey on the Radio?” chooses an unlikely conduit, a musically trained seal, through which to understand a seminal moment in the evolution of radio. Starting in January 1941, broadcasters boycotted an exorbitant raise in song royalties and, by doing so, altered the course of popular music. The episode does an excellent job of drawing out a long chain of events that started with the earliest days of songwriting and then drops you off comfortably in 2015. As a series of audio documentaries on the music industry, Between the Linear Notes is taking shape as a project that burns the midnight oil researching its material. It calls to mind the research put into podcasts like You Must Remember This, Memory Palace, and Lore—lofty company, to be sure. Like those podcasts, BLTN dares to be epic when other franchises are content to skew slice-of-life.